In order to change the scenery in a theatre, it is common practice to use moving apparatus comprising an operating line having its end fastened to a carriage that is connected to the load by a carrier cable. With theatre scenery, the apparatus has a plurality of carrier cables, each having one end connected to the carriage, with their opposite ends being connected at various points to a beam carrying the scenery. In order to make moving easier, it is known to use counterweights that are fastened to the carriage and that are of weight equal to the weight of the load. That structure makes it easy to move the load manually by means of the operating line. Nevertheless, when it is necessary to change scenery of given weight, for other scenery of weight that is different from that of the preceding scenery, it is necessary to adapt the counterweight correspondingly so that the counterweights and the load have the same weight. That operation is arduous and requires several people to be present.
In order to avoid that drawback, it is known to replace the operating line and its counterweight with an electric motor that is fastened to the floor. Nevertheless, the weight of a piece of theatre scenery can be very high (up to 300 kilograms (kg)), such that replacing counterweights by an electric motor involves using an electric motor of large size, which is generally not compatible with the space available, and which is of high cost.